I've only seen RoS once, and I was completely hammered, but I came out of the theater with an overall positive feeling on the movie. I think it was a lot better then it had any right to be coming after TLJ.
Yes, the movie completely retcons TLJ. You could literally watch TFA and skip to ROS and barring one or two things you wouldn't be lost on anything at all.
Yes, the movie was acceptable but bland. If you were expecting anything else after TLJ I would honestly be surprised. For one thing JJ's entire reputation as a director is making safe media. The only reason he was given Star Wars was because of his work on Star Trek. And what did he do with Star Trek? He took a dying franchise that was slipping out of the public consciousness and made movies so perfectly "okay" that it revived interest in the franchise. That's what he was brought in to do with Star Wars. Coax over the public outrage toward the dogshit prequels, create a blank canvas for others to work on, and then hand over the reins to someone else. Disney didn't calculate Rian ****ing up the franchise so badly though, so JJ had to come back to coax over the fanbase a second time. He's basically the king of fan service.
And it worked, for me at least. By the time we got to the ending of the movie I was thinking to myself "you know, I'd be interested in seeing more Star Warsy stuff now that this story is concluded". I had the exact opposite feeling after TLJ. If no Star Wars media had ever been created again I would have been perfectly fine with it.